Centrifugal evaporator



April 28, 1959 E. BROWNELL 2,884,050

CENTRIFUGAL EVAPORATOR Filed March 25, 1954 v 2 Sheets-Sheet l INVENTOR.

I [Z 4 27,52 (.92 E 5 United States Patent CENTRIFUGAL EVAPORATOR LloydE. Brownell, Ann Arbor, Mich.

Application March 23, 1954, Serial No. 418,006

7 Claims. (Cl. 159--6) This invention relates to a centrifugalevaporator of the type particularly adapted for concentratingradioactive solutions or for evaporating sea water.

An object of the invention is to provide an improved and highlyefficient method and apparatus for evaporating liquids, particularlyaqueous solutions, in sltuatlons where an uncontaminated vapor isdesired as the end product, as for example in concentrating radioactivesolutions wherein entrainment of particles of the liquor with the vaporduring the evaporation process must be pos1- tively avoided, or as forexample in the evaporation of sea water to produce distilled water.

Another object is to provide a centrifugal evaporator which isparticularly compact and simple in construction and substantiallynoiseless in operation, thereby being readily adaptable for use on boardships, particularly submarines during wartime, wherein compactness andquietness of operation are of great importance.

In the concentration of radioactive solutions, it is frequentlydiflicult for maintenance personnel to approach the evaporator becauseof radiation. It is accordingly another object of the invention toprovide an improved vertical type centrifugal evaporator which is selfdraining when not in use and which employs self draining liquid sealsbetween the rotating and stationary parts, the seals requiring little orno maintenance and being particularly effective when the evaporator isin operation.

Other objects are to provide a method and apparatus of the foregoingcharacter wherein the liquor to be evaporated is fed by centrifugalforce to the inner surface of a rotating cylindrical heat exchanger, andwherein steam is applied directly to the outer surface of the heatexchanger to heat the same. The liquor is maintained in a thin film orlayer on the inner heat exchanger surface and is rapidly moved axiallytherealong from the inlet or feed area by the centrifugal force.

By virtue of the foregoing, the centrifugal force prevents thecollection of condensate on the outer or steam side of the cylindricalheat exchanger, achieving a high coeflicient of heat transfer theretofrom the steam. The high velocity of axial movement obtained by theliquor film on the inner side of the heat exchanger results in a highcoeflicient of heat transfer from the heat exchanger and through theliquor. The latter coefficient is materially enhanced by the intimatecontact achieved between the liquor and heat exchanger by reason of thecentrifugal force acting on the liquor film, whereby a high rate ofevaporation without the formation of bubbles either below or on thesurface of the liquor is readily achieved. In addition entrainment ofliquor particles with the vapor, which ordinarily results from therupturing of bubbles at the surface of a boiling liquid, is positivelyavoided. If some cause such as splashing of the liquor as it is fed tothe evaporating area results in droplets being thrown into the vaporspace, these droplets are thrown back to the liquor film by thecentrifugal force before the vapor leaves the evaporating area.

Another object is to provide an improved centrifugal 2,884,050 PatentedApr. 28, 1959 ice specification wherein like reference charactersdesignate corresponding parts in the several views.

Fig. 1 is a fragmentary elevational view of an evaporator embodying thepresent invention, portions being shown in vertical mid-section toillustrate details of construction.

Fig. 2 is a fragmentary elevational view of a modification of thepresent invention, portions being shown in vertical mid-section toillustrate details of construction.

Fig. 3 is a vertical section taken in the direction of the arrowssubstantially along the line 33 of Fig. 2.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring particularly to Fig. l, a vertical type centrifugal evaporatoris shown comprising an outer generally cylindrical shell or housing 10having in the present instance upper and lower cylinder portions 10a and10b respectively. The portion 10b is provided with a number of footingsll adapted to be secured to a foundation by bolts 12, whereby thehousing 10 is firmly supported, and is enlarged at its upper end tocomprise the lower and outer walls of an annular radially inwardlyopening liquid seal channel 13. The upper wall of the channel 13comprises an annular flange 16 of the cylinder 10a secured to the edge14 of the cylinder 1012 by bolts 15. The lower wall of the channel 13extends radially inwardly beyond the inner circumference of the flange16 and cylinder 10a and terminates in an upturned annular flange 13a.

Upper and lower end closure plates 17 and 18 respectively close the endsof the housing 10 and are secured to annular flanges 19 and 20 at theupper and lower ends of the cylinders 10a and 10b respectively by bolts21. Suitable gaskets 22 interposedbetween the paired flanges 14, 16 and17, 19 and 18, 20 complete steam tight seals. Rotatable coaxially withinthe chamber 10 is a tubular nner shell or heat exchanger 23 having asmooth vertical inner cylindrical surface 23a and an outer cylindricalsurface spaced from the inner circumference of the flange 13a. A radialouter shoulder 24 below the upper end of the heat exchanger 23 providesan annular seat for the lower wall of an annular radially inwardlyopening channel member 25, the upper wall of the latter extendingradially inward and being keyed to a vertical drive shaft 26 coaxialwith the cylindrical shells 10 and 23. The juxtaposed portions of themember 25 and flange 24 are provided with a sealing gasket 27therebetween and are clamped tightly together by bolts 28, the upperedge of the heat exchanger 23 being flush with the upper surface of thelower channel wall of the member 25 and comprising an inward extensionthereof to complete an annular liquid feed seal channel 29.

The shaft 26 is journaled at its upper and lower ends in bearings 30 and31 seated within the plates 17 and 18 respectively and is maintained inaxial position by retainer nuts 32 and 33 screwed snugly against saidbearlugs. 26 is a feed bore 34 having a conically restricted upper inlet35. Above the base of the bore 34 and spaced below Opening coaxiallyinto the upper end of the shaft the upper wall of the member 25 by anannular spacer 36 are a plurality of radial feed distributing ducts 37.The latter comprise tubular conduits having radially inner ends incommunication with the bore 34 and secured to the shaft 26 at locationsspaced uniformly around its circumference, their outer ends opening intothe annular channel 29 outwardly of the surface 23a.

Steam is supplied to the steam chamber or space between the shells and23 and directly to the exterior surface of the heat exchanger shell 23via a steam inlet duct 39 which opens radially into housing 10. Theupper and lower ends of the steam chamber are determined by upper andlower liquid seals formed by rotating condensate water at high speedwithin the annular channel 13 and an upper annular water seal channel40. The latter opens radially inwardly and is formed between the topplate 17 and an annular flange 41 integral with the shell 10 andextending radially inwardly therefrom at a loca tion spaced somewhatbelow the plate 17. The inner periphery of the flange 41 turns upwardlyin an annular flange 41a spaced outwardly from the shaft 26 to permitupward passage of steam around the shaft 26. One or more small weepopenings 42 in the flange 41 drain condensate from the channel 40 whenthe evaporator is not in operation.

In order to effect the water seals, a pair of impeller wheels 43 and 44keyed coaxially on the shaft 26 extend radially into the channels 13 and40 respectively. Each wheel is provided with a plurality of radiallyextending impeller blades at its periphery, whereby condensate on thewheels or within the channels 13 and 40 is thrown to the outer walls ofthese channels by centrifugal force when the shaft 26 is rotated.Draining of condensate from the steam chamber is accomplished via adrain conduit 45 which opens through the bottom wall of the channel 13and extends outwardly through the cylinder 10 to a condensate sump.

The shaft 26 is powered by a motor 46 supported on a platform 47 mountedon the exterior of the cylinder 10. A drive pulley 43 keyed on the driveshaft 49 of motor 46 is coupled by means of pulley belts 50 with adriven pulley 51 keyed on shaft 26, whereby the latter is rotated athigh speed upon operation of motor 46.

In order to discharge vapor from the heat exchanger shell 23, the latterextends somewhat below the impeller wheel 43 and opens at its lower endinto the cylinder 10!) which is in communication with a vapor dischargeconduit 52. The lower end of the shell 23 extends into an annular liquidseal channel 53 which opens axially upwardly within the cylinder 1%. Thechannel 53 comprises an annular base flange 53a integral with thecylinder 10b and extending radially inwardly therefrom at a locationspaced below the lower edge of the shell 23. Inner and outer annularflanges 53c and 53b spaced from the shell 23 and integral with the baseflange 53a extend upwardly therefrom above the lower edge of the shell23 at opposite sides thereof, the outer flange 53b being also spacedinwardly of the cylinder 10b and having a weep opening 54 near itsbottom edge to permit draining of the channel 53 when the evaporator isnot in use.

The opening 54 opens into the annular space between the flange 53b andcylinder 10b, which space in turn discharges via conduit 55 incommunication with the interior of the cylinder 10b at a locationimmediately above the base flange 53a. Adjacent and above the sealchannel 53 are two or more small pressure equalizer conduits 54aextending radially through the shell 23 at locations spaced uniformlyaround the latters circumference, thereby to prevent surging of liquidin channel 53.

Spaced somewhat above the bottom plate 18 is an annular flange 56integral with the cylinder 10 and extending radially inwardly therefromto comprise in cooperation with the plate 18 and shell 10b a radiallyinwardly opening bottom liquid seal channel 57.

Keyed coaxially on the shaft 26 is a bottom impeller wheel 58 whichextends radially into the channel 57 and is provided at itscircumference with a plurality of blades for rotating condensate withinthe channel 57 to effect a vapor seal therein in the manner of the sealsin channels 13 and 40. In order to drain excess condensate from thebottom of the cylinder 10b, a discharge conduit 59 opens into thechannel 57 through the bottom plate 18 at a location radially inward ofthe impeller blades on the wheel 58. In the present instance theconduits 55 and 59 converge to a common duct from which the concentrateand condensate are recirculated through the evaporator if desired.

By virtue of the above described structure, when motor 46 is operated torotate pulley 51, shaft 26 and the heat exchanger 23 are rotated as aunit, together with the impellers 43, 44 and 58, feed seal channel 29and feed ducts 37. Dilute liquid to be concentrated, such as aqueousradioactive waste for example, is fed into the upper end of bore 34 viaa feed conduit 60 while shaft 26 is rotated at sufficiently high speedto effect a centrifugal force at the surface 23a amounting to an orderof magnitude approximating a thousand times the force of gravity. Forconcentrating sea water or dilute aqueous radioactive solutions, acentrifugal force in excess of 600g is preferred in order to obtainoptimum evaporating and heat transfer conditions, including a high speedof axial flow of a thin aqueous film along the surface 23a and theavoidance of bubble formations. Greater centrifugal forces will beemployed to prevent boiling of solutions more volatile than water and toassure a rapid axial flow of solutions more viscous than Water.

Any tendency for the incoming liquor to splash out of bore 34 isprevented by the upper conical dam at the inlet 35. The liquor is forcedradially out of tubes 37 by centrifugal force into channel 29 whichserves to prevent splashing and to trap suspended solids which mightotherwise collect on the heat transfer surface 23a. The tendency tosplash is minimized by the fact that the channel 29 and liquor therein,together with tubes 37, all rotate at the same angular speed.

The channel 29 also serves to spread the incoming liquor uniformlyaround the inner circumference of the heat exchanger 23. As the liquoroverflows the lower wall of the channel 29, it is spread by thecentrifugal force in a thin film over the surface 234:, causing theliquor in advance thereof to flow rapidly downwardly toward channel 53.

Simultaneously, steam entering inlet 39 will heat the outer surface ofthe heat exchanger 23, causing evaporation of the liquor without boilingfrom the film or layer covering surface 23a. The resulting vapordischarges through outlet 52 at a location remote from the trap 29.Bubble formation canont take place either adjacent the hot surface 23aor at the inner surface of the liquor film because the centrifugal forcepresses the liquor against the heat transfer surface 23a. Inasmuch asthe coefficient of heat transfer to the liquor film is proportional to afunction of the velocity of the film over the heat transfer surface, thecoefficient of heat transfer is increased by the rapid downward flow ofthe liquor film urged along surface 23a by the centrifugal force. Thelatter exceeds the gravity force by such a large factor that theinfluence of the latter force is negligible.

The concentrated liquor collects in channel 53 and overflows into duct55 because the height of inner flange 530 is greater than the height offlange 53b. In order to prevent passage of the liquor through thepressure equalizer duct 540, the latter projects radially inwardly farbeyond the liquor film. The loss of a small amount of vapor through duct54a is negligible. The liquor con centrate in channel 53 and condensatecirculated in channel 57 by impeller 58 prevent losses of vapor.

Steam condensing against the outer surface of the heat exchanger 23 isimmediately thrown therefrom by the centrifugal force. Thus the outersurface of shell 23 is maintained substantially dry and in intimatecontact with the live steam, achieving optimum heat transfer. Condensaterotated in the channels 13 and 40 by the impellers 43 and 44 effectseals in these channels which limit the axial steam flow Fig. 1illustrates a vertical single effect evaporator construction which isadvantageous in concentrating radioactive solutions. In handling suchsolutions simplicity and compactness are more important than steameconomy, so that only a single evaporating effect is illustrated. Alsothe vertical unit shown drains more readily than a horizontal unit whennot in use and is accordingly more satisfactory for handling radioactivesolutionsf It is to be noted however that the primary operational forcesare centrifugal, so that a horizontal or inclined unit would besatisfactory in other applications. In any case the present processcomprises feeding the liquor by centrifugal force to the innercylindrical surface of a rapidly rotating heat exchanger wherebycentrifugal force rapidly moves the liquor in a thin film or layeraxially from the feed area to a collection area. At the same time, theouter surface of the heat exchanger is heated by steam, wherebycondensate is thrown by the centrifugal force from said outer surface tomaintain a high heat transfer coeflicient between the steam and heatexchanger. The heat is conducted to the inner surface of the heatexchanger and thence to the liquor film to cause evaporation, thecentrifugal force preventing bubble formations thereby to avoidentrainment of liquid particles in the vapor and to effect incooperation with the rapid axial movement of the liquor film a highcoefficient of heat transfer to the liquor.

Referring to Figs. 2 and 3, a triple efiect horizontal evaporator isillustrated which is particularly suitable for concentrating sea Water,by Way of example, although the unit is suitable for other industrialapplications. The structure comprises an outer horizontal cylindricalshell or housing 70 mounted on footings 71 and secured to a firm supportby bolts 72. End closures 73 and 74 are bolted to the ends of the shell70 by bolts 75.

The end closure 74 is provided with a large central opening 76 and issuitably secured by bolts 77a to a fluid seal housing assembly indicatedgenerally by the numeral 77, which completes a drum-like vapor chamberwithin the shell 70. The assembly 77 is formed to comprise incooperation with the end closure 74 an annular radially inwardly openingliquid seal channel 78 having an outer annular sidewall 79 extendingradially inwardly beyond the opening 76. Spaced axially endwise of thechannel 78 is a similar annular liquid seal channel 80 formed in theassembly 77.

Extending coaxially through the housings 70 and 77 is a rotatable driveshaft 81 journaled adjacent opposite ends in bearings 82 and 83 mountedin the end closure 73 and housing 77 respectively. The shaft is rotatedat high speed by means of a motor 84 supported on a platform 85 securedto the end closure 73. The motor 84 is operatively coupled with theshaft 81 by pulley belts 8c entrained around pulleys 87 and 88 keyedcoaxially on the motor shaft 89 and drive shaft 81 respectively.

In the present instance, the space within housing 70 is partitionedaxially into three separate evaporating effects A, B, and C bypartitions rotatable as a unit with shaft 81. These partitions include ahub or annular plate 90 keyed to shaft 81 and spaced axially inwardlyfrom end closure 73 to comprise the outer boundary of effect C.Extending radially through an axially inwardly thickened rim 91 of plate90 are a plurality of liquor discharge bores or tubes 92 opening attheir inner ends within the effect C and at their outer ends uniformlyaround the periphery of plate 90. Integral with the rim 91 and extendinginwardly therefrom coaxially with shaft 81 at a location radiallyoutward of the inner periphery of the rim 91 is a cylindrical tube sheetor plate 94 which comprises a horizontal boundary partition for effectC. The

inner end of plate 94 terminates in an annular plate 95 which extendsradially outwardly from the plate 94.

Spaced axially inwardly from plate 95 to provide a vapor passage fromeffect C into a second condensing chamber E is a hub or plate 96 keyedto shaft 81 and comprising a vertical partition between effects B and C.Also similar to plate. 94 is a cylindrical tube plate 97 integral withplate 96 and extending leftward from the outer periphery thereofcoaxially with shaft 81 to comprise a horizontal partition betweeneffect B and chamber E. The plate 97 terminates at its left edge in anannular plate 98 similar to plate 95 and extending radially outwardlyfrom plate 97 to comprise a vertical left boundary for chamber E. Theplate 95 comprises a vertical partition between chambers D and E.

Spaced axially outwardly from plate 98 to provide a vapor passage fromeffect B into a third condensing chamber F is an annular hub or plate 99keyed to shaft 81 and comprising a vertical partition between effects Aand B. A cylindrical tube plate.100 integral with plate 99 extendsoutward therefrom coaxially with shaft 81 to comprise a horizontalpartition between effect A and chamber F and terminates in an annularplate 101 comprising a vertical outer boundary for chamber F.Cylindrical closure plates 102 and 103 coaxial with shaft 81 are securedby bolts 104 to the outer ends of plates 95, 98 and 101 to comprise thecircumferential boundaries for chambers E and F respectively.

In operation of the structure described thus far, the motor 84 isoperated to rotate shaft 81 at high speed, thereby to rotate the hubs90, 96 and 99, together with the connected partition structure, theouter housings 70 and 77 remaining stationary. Liquor to be concentratedis fed from a stationary supply conduit 105 into a feed bore 106extending axially into the left end of shaft 81. This liquid isaccelerated to the angular velocity of the shaft, and, until it leavesthe evaporator, is only contacted by rotating parts of the latter. Aconical dam 107 machined on the inner surface of the bore 106 adjacentthe latters outer end prevents back flow of the liquor from the shaft.Centrifugalforce causes the liquor to flow out of two or more radialfeed nozzles 108 into an annular radially inwardly opening liquid sealchannel 109 integral with plate 100. The nozzles 108 are spaceduniformly around shaft 81 and are secured thereto at their inner ends incommunication with bore 106. The outer ends of the nozzles 108 extendinto channel 109 which latter thus comprises a splash trap. The annularouter sidewall of channel 109 extends radially inwardly more than doesthe annular inner sidewall of channel 109, so that fluid entering thelatter channel from nozzles 108 will overflow onto plate 100.

In order to increase the heat transfer area as described below, theliquid in each effect is forced to travel through hairpin or U-shapedtubes 110 having radially inner ends rolled into the cylindrical tubeplates or sheets 94, 97 and 100. The loops of the tubes 110 extendradially outwardly into the condensing chambers D, E and F. As indicatedin Fig. 3, the tubes 110 are spaced uniformly around the circumferenceof the tube sheets, but the spacing between adjacent tubes isexaggerated in the drawings for the sake of simplicity. By way ofillustration, two annular sets of tubes 110 are shown opening into eachof effects A and B, whereas one annular set of tubes 110' open intoeffect C. The open ends of each tube 110 are are spaced axially,separated by annular bafiles 111 extending radially inwardly from thetube plates, so that the liquid is forced to flow in series through thetubes 110 of the successive annular sets as it progresses axially fromleft to right. Fig. 2 illustrates the condition wherein a portion of theliquid in each effect A and B travels through two tubes in series topass from its point of entry to its point of discharge. The remainder ofthe liquid feed may be baflled to pass in either a series or a parallelmanner through the other tubes similarly located about the circumferenceof the cylindrical tube sheets. The velocity of the liquid in the tubes110 is controlled by the rate of feed into bore 106 and by the bafflearrangement. The maximum velocity is obtained by baffling between eachtube so as to force the liquid to travel in series through all the tubes110 in a circumferential as well as in axial progression. Semi-circularinserts 114 machined to fit the inner side of the hairpin loops preventsdistortion of the tubes 110 during rotation.

As the liquid flows through the hairpin tubes 110, it is heated by vaporcondensing on the ouside of the tubes, as described below. However, thehigh pressure on the liquid exerted by centrifugal force preventsboiling in the tubes. Evaporation occurs on the surface of the liquidwhere the pressure is the least. After rising in portion 113 of effectA, the partially concentrated liquid leaves the first effect viaoverflow tube 115 which passes through plate 99 into the next effect B.Since the overflow tube 116 for effect B is spaced radially outward fromthe axis of shaft 81 a greater distance than overflow tube 115, thesurface of the liquid in effect B is subjected to a greater centrifugalforce than the surface of the liquid in the previous effect A and thevapor pressure in effect B will be correspondingly greater than ineffect A. The liquid again passes through the hairpin tubes 110 ineffect B as in the previous effect and discharges through plate 96 viathe overflow tube 116 into the last effect C. The liquid from the lasteffect C overflows through bores 92 into a stationary radially inwardlyopening annular channel 117 having the outer periphery of rim 91projecting thereinto. The latter is provided with impeller blades forrotating the concentrate in channel 117 to provide a liquid seal thereatin the manner of the seals in channels 13, 29, and 57. The channel 117is integral with the end closure 73 and has an annular inner sidewallextending radially inwardly almost to the outer surface of plate 94. Aconcentrate outlet 118 opens into channel 117 through the end closeure73 at a location intermediate the base of channel 117 and the innerperiphery of the inner sidewall of channel 117, whereby the concentratedliquor overflows into outlet 118 rather than into chamber D.

It is to be noted that the radial distances of the inner ends of theoutlet bores 92 from the axis or shaft 81 are greater than thecorresponding radial distance to the outlet 116, which in turn isgreater than the corresponding radial distance to outlet 115, and thelatter distance is greater than the corresponding radial distance to theinner circumference of the annular inner sidewall of channel 109. Thusthe liquor level indicated by the dotted horizontal lines in Fig. 2 willbe at a location subject to a maximum centrifugal force in effect C, anintermediate centrifugal force in effect B, and a minimum centrifugalforce in effect A. The baffles 111 in each effect extend radiallyinwardly beyond the liquor level in the associated effect. Likewise theplates 95 and 98 also project radially inwardly beyond the liquor levelin the effects C and B respectively.

Referring now to the vapor side of the evaporator, steam at the desiredoperating pressure enters condensation chamber D through nozzle 119 andcondenses on the tubes 110 in the latter chamber. The centrifugal forcethrows the condensate from the tubes 110, maintaining a high condensingfilm coefficient of heat transfer. Heat transferred to the liquid causesevaporation in effect C, but at a lower temperature and pressure thanthe steam in condensing chamber D. The vapor from effect C enterscondensing chamber E and condenses on the cooler tubes H therein. Thecondensate is thrown to the rorating wall 102 where it accumulates untilsutficient pressure permits its escape through a spring loaded valve120. The foregoing process is repeated in the first effect A. Heat fromvapor condensing in chamber E releases vapor at lower temperature andpressure in effect B. Vapor from effect B condenses on the cooler tubesin chamber F and is thrown to wall 103, from which the condensate isreleased through a spring loaded valve 121. The condensate from allthree condensing sections is discharged through nozzle 122 at the bottomof housing 70.

The vapor from the first effect A passes axially between the rotatingfeed tubes 108 and is discharged through vapor outlet 123 openingradially into housing 77 at a location intermediate the liquid sealchannels 78 and 80. This vapor is condensed in a condenser separate fromthe evaporator and added to the condensate from nozzle 122. The latternozzle is in communication with steam entering from nozzle 119, butsteam loss is blocked by a suitable steam trap in the discharge conduitfrom nozzle 122.

An impeller wheel 124 keyed on shaft 81 and having peripheral impellerblades rotating in channel rotates condensate therein to effect a liquidseal and prevent loss of vapor from effect A. Similarly an impellerwheel 125 having blades rotating in channel 78 rotates condensatetherein to effect a liquid seal and prevent loss of steam entering viainlet nozzle 119. At the other end of the housing 7 fl, passage of steamfrom chamber D is blocked by the liquid seal in channel 117. Althoughthe preferred liquid seals are disclosed herein, conventional packingseals fill be employed in accordance with the requirements of otherapplications.

By virtue of the structure described, the direction of vapor flow iscontrary to the direction of liquor flow and is baffled or interruptedso as to avoid a continuous rapid vapor flow and the possibility ofentrainment of liquor that would otherwise result in a rapid vapor flow.Thus steam in chamber D is isolated from chambers E and F and from theevaporating effects A, B, and C. Vapor in effect C can pass to chamberE, but is isolated from effect B in chamber F. Vapor in effect B canpass to chamber F, but is isolated from effect A, which exhausts viaoutlet 123. The centrifugal force on the liquor surface in effects A, B,and C achieves evaporation without boiling, thereby positively avoidingan additional cause of entrainment.

I claim:

1. In a centrifugal evaporator for concentrating liquids and preventingentrainment of non-vapor particles in the evaporate, rotatable heatexchanger means comprising a multiple effect evaporator, the evaporatingeffects being in axially spaced succession along a common axis ofrotation and sealingly partitioned from each other against vapor flow,each effect comprising a radially inwardly opening trough adapted tohold liquid therein when said heat exchanger means is rotated about saidaxis, means for feeding liquid into the trough of the first effect ofsaid succession, means for feeding liquid from each effect into the nextsuccessive effect comprising an Outlet for each trough connected withthe trough of the next successive effect, the radial distance from saidaxis to the outlet of the trough in each effect being shorter than thecorresponding radial distance in the next successive effect, liquordischarge means in communication with the outlet of the last effect insaid succession, a vapor passage from each effect, except the first, toa condensing chamber in heat exchange relationship with the nextpreceding eflect, with regard to liquid flow and heating means forheating said heat exchanger means to evaporate liquid therein.

2. In a centrifugal evaporator for concentrating liquids and preventingentrainment of non-vapor particles in the evaporate, a rotatable shaft,a succession of evaporating effects spaced axially along the axis ofsaid shaft, means partitioning each effect from the others, each effectcomprising a trough opening radially inwardly with respect to said axisand connected to said shaft to rotate therewith, thereby to containliquid therein by centrifugal force upon rotation of said shaft, meansfor feeding liquid by centrifugal force into the trough of the firsteffect of said succession comprising axially extending liqnor conduitmeans within said shaft to rotate therewith and arranged symmetricallywith respect to said axis, said conduit means having an inlet openingaxially at one end and also having an outlet located radially outwardlyfrom said inlet and in communication with the last named trough, meansfor feeding liquid from each elfect except the last into the nextsuccessive effect comprising an outlet for each trough connected withthe trough of the next successive efiect, the radial distance from saidaxis to the outlet of the trough in each effect being shorter than thecorresponding radial distance in the next successive effect, liquordischarge means in communication with the last effect in saidsuccession, and heating means for heating said heat exchanger means toevaporate liquid therein.

3. The combination in a centrifugal evaporator as set forth in claim 2wherein said liquor conduit means includes a trough opening radiallyinwardly with respect to said axis adjacent the trough of said firsteifect, the latter two troughs having a common partition terminatingradially inwardly at locations spaced radially outwardly from saidinlet.

4. In a centrifugal evaporator for concentrating liquids and preventingentrainment of non-vapor particles in the evaporate, a rotatable shaft,a succession of evaporating eifects spaced axially along the axis ofsaid shaft, each effect comprising an annular trough coaxial with saidshaft and opening radially inwardly with respect thereto, one sidewallof each trough extending radially inwardly to said shaft and beingconnected thereto and comprising a partition wall for the associatedevaporating effect, a radially inwardly opening annular feed seal troughcoaxial with said shaft, the axially inner sidewall of the feed sealtrough comprising the axially outer sidewall of the trough of the firsteffect relative to liquid flow and extending radially inwardly a lesserdistance than the axially outer sidewall of said feed seal trough, aradial tubular feed duct extending radially from said shaft andconnected thereto to rotate therewith, the outer end of said feed ductextending into said feed seal trough to discharge liquor thereinto, afeed supply duct extending axially into said shaft and being incommunication with said radial feed duct, means for feeding liquid fromeach effect into the next successive effect relative to liquid flowcomprising an outlet for each trough connected with the trough of thenext successive effect, the radial distance from said axis to the outletof the trough in each effect being shorter than the corresponding radialdistance in the next successive effect, liquor discharge means incommunication with the outlet of the last effect in said succession, asuccession of condensing chambers contiguously associated with saidevaporating effects respectively, a first condensing chamber withrespect to vapor flow being associated with the last evaporating effectrelative to liquid flow and vice versa, means partitioning each chamberfrom the other chambers, a portion of the trough of each effectcomprising a heat exchange surface partitioning that effect from theassociated condensing chamber, vapor conduit means connecting eachcondensing chamber except the first with the evaporating efiectassociated with the next preceding condensing chamber relative to vaporflow, vapor inlet conduit means opening into the chamber at one end ofsaid succession of chambers, and vapor outlet conduit means opening fromthe evaporating effect associated with the chamber at the other end ofsaid succession of chambers.

5. The combination in a centrifugal evaporator as set forth in claim 4wherein said one sidewall of the trough of each effect being thesidewall of that trough axially remote from said feed seal trough, theother sidewall of the trough of each effect being spaced from said oneside- Wall of the trough of the next preceding effect in the directionaxially away from said feed seal trough and the spacing betweenjuxtaposed troughs of the successive elfects comprising said vaporconduit means, the trough of each effect also having a portion extendingradially outwardly from adjacent said other sidewall thereof andcomprising a radial sidewall of said means partitioning each chamberfrom the other chamber, the latter means also comprising a cylindricalpartition spacing and connected to the radially outer edges of adjacentpairs of the radial sidewalls, and said vapor inlet conduit means opensinto the chamber associated with the last evaporating effect relative toliquid flow in said succession of effects.

6. The combination in a centrifugal evaporator as set forth in claim 1wherein said heating means comprises a succession of condensing chamberscontiguously associated with said evaporating effects respectively, thefirst condensing chamber with respect to vapor fiow being associatedwith the last evaporating effect with respect to liquid flow andvice-versa, a portion of the trough of each effect comprising a heatexchange surface partitioning that evaporating elfect from itscontiguously associated condensing chamber; vapor conduit meansconnecting each condensing chamber except the first with the evaporatingeffect associated with the next preceding condensing chamber relative tovapor flow; and vapor inlet conduit means opening into the firstcondensing chamber; and a vapor outlet opening in the first evaporatingetfect.

7. The combination in a centrifugal evaporator as set forth in claim 3wherein said heating means comprises a succession of condensing chamberscontiguously associated with said evaporating effects respectively, thefirst condensing chamber with respect to vapor flow being associatedwith the last evaporating effect with respect to liquid flow and viceversa, a portion of the trough of each effect comprising a heat exchangesurface partitioning that evaporating effect from its contiguouslyassociated condensing chamber; vapor conduit means connecting eachcondensing chamber except the first with the evaporating effectassociated with the next preceding condensing chamber relative to vaporflow; and vapor inlet conduit means opening into the first condensingchamber; and a vapor outlet opening in the first evaporating efiect.

References Cited in the file of this patent UNITED STATES PATENTS1,420,648 Mabee .Tune 27, 1922 1,588,029 Kermer June 8, 1926 2,124,914Fottinger July 26, 1938 2,292,483 Rowell Aug. 11, 1942 2,551,360Bierwirth May 1, 1951 2,596,875 Stewart May 13, 1952 2,623,580 ArnaudDec. 30, 1952 2,668,080 Peebles et al. Feb. 2, 1954 FOREIGN PATENTS5,143 Great Britain 1878

